Conventionally, microfabrication techniques based on lithography are employed in manufacturing processes of semiconductor devices such as LSI. In the future, a much finer processing is certainly required. Accordingly, shortening the wavelength of a light source in lithography and enhancing performance of a resist are proceeding. However, it is becoming difficult to improve resolution by these measures.
On the other hand, a microfabrication technique using a phase-separated structure of a block copolymer attracts attention. In this microfabrication technique, it is required to regularly arrange the phase-separated structure of the block copolymer. In order to regularly arrange the phase-separated structure of the block copolymer, following methods are proposed.
For example, known is a method comprising: forming a self-assembled monolayer (SAM) on a substrate; applying a resist thereto followed by forming line-and-space resist patterns by lithography; selectively irradiating the SAM with X-rays in an oxygen atmosphere using the resist patterns as masks to chemically modify a part of the SAM; removing the resist patterns; and applying a block copolymer to the SAM followed by annealing to form microdomain patterns of the block copolymer.
Also, known is a method comprising: forming an SAM on a substrate; selectively exposing a part of the SAM by interference exposure with two or more beams to form chemically modified dot patterns; and applying a block copolymer to the SAM followed by annealing to form contact hole patterns through phase separation of the block copolymer.
Furthermore, known is a method comprising: forming an SAM on a substrate; applying an electron beam resist thereto followed by forming dot patterns by lithography; irradiating the SAM with oxygen plasma using dot patterns of the electron beam resist as masks to chemically modify a part of the SAM; removing the resist patterns; and applying a block copolymer to the SAM followed by annealing to form microdomain patterns of the block copolymer. In this method, it is disclosed that a dot pitch of the dot patterns of the block copolymer may be narrower than that of the dot patterns formed in the electron beam resist.
However, these methods require many steps to align the orientation of the microdomain patterns of the block copolymer and thus they are impractical for the microfabrication techniques for semiconductor devices.